1. Field of the Invention
The present invention relates to electrically powered motors, and in particular, to stators.
2. Description of the Related Art
Electrically powered motors to date have been furnished with a stator, and with magnetic-field producing magnets, which are the drive part that rotates a motor's rotor section relative to its stator section. Stators include an annular core, insulators as non-conducting components that cover teeth sections of the core, and coils formed by wrapping conductors onto the insulators. In midsized motors such as are used for “electric power steering systems” (as termed in, for example, U.S. patent application Pub. No. 2002/0175574, but also referred to as “steer-by-wire systems”), conductors of relatively large diameter are wrapped around insulators and employed as the coils.
In such motors, owing to the fact that motor efficiency increases with conductor diameter, technology for improving the slot-fill factor of the coils by wrapping on the conductors in regular rows without gaps is paramount. In the present specification, the term “space factor” (as termed in, for example, paragraph [0006] of both U.S. patent application Pub. No. 2004/0263015 and patent application Pub. No. 2005/0029894, but also referred to as “slot-fill factor,” or “slot-fill ratio”) is intended to mean the ratio of the area occupied by the conductors with respect to the cross-sectional area in the interval (slot) between adjoining stator teeth.
In stator implementations employing large-diameter conductors that do not bend readily, when the conductors are wound onto the teeth, it can happen that a conductor, as wrapped onto a tooth from one flank to the other flank, does not bend fully around a terminus of the tooth, and is instead left riding up off the tooth, not lying in full contact along the flanks. For example, in stator implementations in which the insulators are formed with tooth-flank guide grooves, it can happen that the conductors fail to be guided by the guide grooves, which is prohibitive not only of attaining evenly-rowed wrapping but also of smooth conductor windings, and limits improvement in the slot-fill factor of the coils.